Power tools

ABSTRACT

The specification discloses a power hand tool, i.e. a tool arranged to be hand held but having a power-driven working element which is arranged to be operated by high-pressure gas produced by the explosion of an explosive charge. The tool includes control means arranged so that the working element can either be impacted and rotated or impacted only or rotated only. In one embodiment of the tool the order in which the working element can be impacted and rotated may be reversed. The preferred explosive charge is a liquid monofuel.

United I States Patent [72] Inventor John Hilton 'hirnbull [56]References Cited p n Severn, land UNITED STATES PATENTS P 2,403,6757/1946 Mitchell 173/107 {22] Filed Feb. 17, 1970 2,824,547 2/1958Sherr1ll 173/106 [45] Patented June 15, 1971 [73] Assi n es GKN screw &Fm M ed 3,403,738 10/1968 Burkhart et al... 144/32 3 e s 3,499,5903/1970 Bayer et a1 227/ Smethwick, Warley, The Plessey Company LimitedPrimary Examiner-James A. Leppink Deiord, England Attorney-Barlow &Barlow [32] Priority Feb. 18, 1969 [33] Great Britain 1 1 551 [54] POWERTOOLS Claims, 5 Drawing Figs.

[52] US. Cl. 173/107, 60/26.]1, 144/32, 227/10 [51] Int." 825d 9/11, Bb21/02 Field of Search 173/106,

ABSTRACT: The specification discloses a power hand tool, Le. a toolarranged to be hand held but having a power-driven working element whichis arranged to be operated by highpressure gas produced by the explosionof an explosive charge. The tool includes control means arranged so thatthe working element can either be impacted and'rotated 01' impacted onlyor rotated only. In one embodiment of the tool the order in which theworking element can be impacted and rotated may be reversed. Thepreferred explosive charge is a liquid monofuel.

H4. log

PATENTED JUN] 5 1971 SHEET 1 OF 3 w H IN! W N HI. N0 V \mmww O6 5 o 0O.0: v:

I. E m: w: Q on wm r NB K 0Q 8m #Q mm. QT m 6 mm 8. Em .2 I m% 1 52 H Ime\ mm, -m mwfl #m k w nu 6. m0 em Q v Q: OQ $6 R. n 3 iii g x W. 3300mm mm o 5 3 mvumx m JOHN HILTON TURNBULL POWER TOOLS 1 Field of theInvention The invention is concerned with power tools which are arrangedto be hand held and are intended for driving fasteners such as screws ornuts.

2. Description of the Prior Art Power hand tools for rotating andimpacting fasteners have already been proposed and manufactured tooperate off compressed air which is normally available in a factory. Thepressure of such air which is normally available however limits theapplication of such tools, so far as they are applied to insertself-tapping and piercing screws, to inserting such screws intocomparatively thin sheet metal. The normal air pressures available areinsufficient to enable the screws to be driven into comparatively thicksections, e.g. steel sections of a thickness of one-eighth inch or more.

It is an object of the present invention to provide a power tool whichwill be capable of inserting self-tapping and piercing screws intocomparative thick sections and which may be controlled so that as wellas providing a rotation and an impact it may provide a rotation only oran impact only.

SUMMARY OF THE INVENTION According to the invention there is provided apower tool comprising a body, a working element mounted on the body forreciprocation and rotation relative thereto an impact member mounted ina first chamber in the body and operable to deliver impacts to theworking element, a rotary drive member mounted in a second chamber inthe body and operable to rotate the working element, receiving means inthe body to receive an explosive charge which, when exploded, produceshigh-pressure gas in one of said chambers; openended passage meansextending between said chambers; and a part on the member in said onechamber which normally covers the end of the passage means in saidchamber but which uncovers said end when said member has been operatedby the high pressure gas to allow the latter to flow along the passagemeans to the other chamber to operate the member mounted therein.

By exploding an explosive charge within the body, gas can be obtainedfor powering the tool at a higher pressure than the normally availablecompressed air. The energy available will thus be capable of effectingwork which cannot be effected with known guns using compressed airnormally available in factories.

The explosive charge may be of any type and may be provided bycartridges or by caseless charges although it is preferred to use aliquid monofuel such as isopropyl nitrate.

The tool may be used for inserting a self-tapping and piercing screw ina workpiece and in this instance the working element comprises ascrewdriver bit.

In an alternative arrangement, the tool can be arranged for running up anut and in this case the working element will be a nut-engaging memberand will be caused to rotate prior to being impacted. A nut may be thusrun .up on a threaded shank and when it has been tightened it may beimpacted and thus locked in position.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described indetail by way of example with reference to the accompanying drawings inwhich:

FIG. I is a section through a tool constituting a first embodiment ofthe invention arranged for inserting a self-tapping and piercing screwin a workpiece and so that the working element is impacted and thenrotated;

FIG. 2 is a section through a tool constituting a second embodiment ofthe invention and arranged so that the working element can be impactedand rotated, impacted only or rotated only;

FIGS. 3A and 3B are diagrams showing the positions of the valve means ofthe tool of FIG. 2;

FIG. 4 is a part section through a tool constituting a third embodimentof the invention in which the order of impact and rotation can bereversed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS.

Referring first to FIG. 1 this shows a tool comprising a body 50 havinga hollow handle portion 51 within which is provided a reservoir 52 for aliquid monofuel eg. isopropyl nitrate. A manually operable pump 53 isprovided on the body to pump the monofuel from the reservoir 52 to adecomposition chamber or breech 54 provided in the body 50.

Slidably and rotatably mounted at one end of the body 50 is a workingelement in the form of a screwdriver bit 55. An impact member 56 isslidably mounted in the body and is arranged to be driven into contactwith the rear end of an anvil 57 as a result of an explosion of themonofuel in the chamber 54 so as to deliver an impact to the screwdriverbit 55. In addition, the gases produced by the explosion are fed to acton a piston 58 connected to a ball nut 59 which causes, when the pistonis driven, the anvil 57 to rotate, thus to rotate the bit 55.

The reservoir 52 is provided with a filler aperture closed by a fillerplug 60 which enables the reservoir to be filled with the monofuel. Atube 61 extends from the bottom of the reservoir 52 into the body 11 andcommunicates with a cylinder 62. A piston 63 is slidably mounted in the:cylinder 62 and has a manually operable piston rod 64 connected theretoat its upper end and is acted upon, at its lower end, by a coilcompression spring 64 which urges the piston 63 upwardly.

The piston 63 is provided with an axially extending passage 66 and twotransversely extending passages 67 and 68 which communicate with thepassage 66 and with the periphery of the piston 63. At the outer end ofthe passage 68 the piston 65 is formed with an axially extending slot69. The body 50 is formed with a passage 70 which extends from theexterior of the body to the wall of the cylinder 62 at a positionintermediate its ends. The body 59 is also formed with a further passage71 extending from the exterior of the body to the bottom of the cylinder62 and a flow-control valve 72 is provided in the passage 71. A passage73 extends from one end of the decomposition chamber 54 to the cylinder62. Sealing rings 74 are carried by the piston 63 and engage the wall ofthe cylinder 62.

The body is formed with a cylindrical bore 75 at its front end 76. Anose piece 77 is mounted on the front end of the body and is providedwith a bearing 78 in which a cylindrical portion 79 of the anvil 57 isslidably and rotatably mounted. The anvil is formed with a circularshoulder 80 and an externally splined spigot 81 which is in nonrotatableengagement with an internally splined clutch member 82 so that the anvil57 and the clutch member 82 can slide axially relative to one anotherbut are constrained to rotate together.

The clutch member 82 has an operative face formed with teeth 83 whichengage teeth 84 on a second clutch member 85. The teeth 83, 84 are soarranged that the clutch acts as a torque-limiting clutch so that ifrotation of the bit 55 and hence of the clutch member 82 is. preventedthe clutch member 85 can slip relative to the clutch member 82. Theclutch member 85 is carried in a holder 86 which is rotatably mounted bya bearing 87 on a boss part 88 of the body.

The external surface of the holder 86 is provided with a helical groove89 of half-circular cross section. Balls 90 are engaged in the groove 89and also engage in a similar groove 91 provided on the nut 59. The nut59 is formed with splines 92 which engage with splines 93 provided inthe bore 75 so that the nut 59 is permitted to move axially in the bodybut is prevented from rotating relative thereto. The piston 58 isannular and slides between the bore 75 and the holder 86, being providedwith seals 94. The piston 58, nut 59 and holder 86 together constitute arotary drive member for the working element or bit 55. Passageways 95are provided between the chamber 54 and the left hand end of the bore 75which provides achamber 75a in which the piston 58 is slidable.

The boss 88 is formed with a cylindrical bore 96 having end walls 97 and98. The end wall 97 is formed with a passage 99 of the same diameter asthe diameter of the decomposition chamber 54 and which constitutes anextension of such chamber. The wall 98 is provided with a bush 100having a bore 101 of the same diameter as the passage 99. The impactmember 56 comprises a piston 102 having a tapered circumferentialsurface 103 of concave form and slidable in the bore 96, a cylindricalspigot 104 slidable in the passage 99 and the chamber 57, sealing means105 being provided between the passage 99 and the spigot member 104, anda spigot 106 slidable in the bore 101 of the bush 100. A coilcompression spring 107 is located in the bore 96 between the end wall 98and the piston 102;, Spring-loaded detents 108 are provided in the wall.

of the bore 96 to engage with the larger diameter part of the shoulderedpiston 102 as hereinafter described in detail.

A manually operable and slidably mounted safety trigger 109 is providedon the body and is formed with a lever spring urged in a slot in thebody. The lever 110 is formed with an inclined face 11011 at the freeend thereof and is engaged within a slot 111 provided in a finger 112slidably mounted in the body for movement into and out of engagementwith the left-hand face of the shoulder 80 of the anvil 57. Acompression spring 113 is provided to urge the finger 112 towards theanvil 57. A compression spring 114 is provided to act between a part 115provided on the holder 86 and the shoulder 80 to urge the anvil 57 tothe right. A further compression spring 116 is provided between theclutch member 82 and said part 115 to urge the clutch member 82 intooperative engagement with the second clutch member 85.

The operation of the tool will now be described assuming that the toolhas previously been operated and that the parts thereof are in thepositions shown in FIG. 1.

After the previous operation the piston 63 of the pump 53 will have beenbiased to its upper position by the spring 65 and a quantity of themonofuel in the reservoir 52 will have been drawn up the tube 61 andinto the cylinder 62 below the piston 63. The amount of monofuel drawninto the cylinder 62 will depend upon how much air is bled into thecylinder 62 through the valve 72 and passage 71 and thus the charge ofmonofuel can be adjusted by adjusting the valve 72.

The piston rod 64 is moved down manually thereby causing the monofuelbeneath the piston 63 to enter the passage 66 past a ball check valve117. As the piston 63 moves downwardly the passage 67 is moved away fromthe end of the passage 70 but because the passage 68 is in communicationwith the slot 69 the passage 68 remains in communication with thepassage 73 and so that a charge of monofuel is pumped through thepassages 68 and 73 to the chamber 54 via a ball check valve 118 in thepassage 73. When the piston 63 has been moved fully downwardly it isreleased and it returns to its normal position under the influence ofthe spring 65 and hence a further charge of monofuel is drawn throughthe tube 61 past a ball check valve 119 and into the cylinder 62 readyfor the next operation of the tool.

A screw, not shown, is engaged with the bit 55 and then the screw isengaged with a workpiece, also not shown, into which it is desired toinsert the screw. The safety trigger 109 is then pressed thus slidingthe lever 110 to the left and causing the face 110a to engage the bottomof the slot 111 and withdraw the finger 112 from engagement with theshoulder 80 on the anvil 57. The tool is then pressed against theworkpiece so that the anvil 57 slides inwardly, thereby compressing thespring 114 and so moving the end 120 of the anvil into engagement withthe end 121 ofthe impact member 56.

Continued urging of the tool towards the workpiece causes the anvil 57to move the impact member 56 to the left thereby disabling the detents108 and so suddenly allowing the impact member 56 to shoot to the leftunder the influence of the spring 107. The sudden movement of the impactmember causes the spigot 104 to project into the chamber 54 thus causingcompression of the gas within the chamber and thus an explosion of themonofuel therein.

The hot gases created by the explosion drive the impact member 56 backto the right against the action of the spring 107 and thus bring theends and 121 into engagement to give the anvil 57 an impact and hencethe bit 55 so that the screw engaged by the bit is driven into theworkpiece and is caused to pierce its own pilot hole in the workpiece.As the spigot 105 moves to the right it uncovers the inner ends of thepassages 95 allowing the gas to flow to the chamber 75a to act on thepiston 58 causing it to move the nut 59 to the right. Since the nut 59cannot rotate, because of the splines 92, 93, the balls 90 in thehelical grooves 89 and 91 cause the holder 86 to rotate, therebyrotating the clutch member 85, the clutch member 83, the anvil 57through the splined connection between the clutch member 83 and theanvil, the bit 55 and hence the screw engaged therewith which is causedto tap the pilot hole it previously formed and is driven into theworkpiece.

When the screw is fully driven, and assuming that this occurs beforerotation of the anvil 57 has ceased, the torque limiting clutch 82, 85operates to enable continued rotation of the holder 86 whilst rotationof the anvil 57 is prevented. The groove 89 is so shaped that the piston58 is caused to return to the position shown in FIG. 1 upon completionof the rotation. A vent 75b is provided which is uncovered by the piston58 at the end of its stroke and allows the gas to escape.

The tool is then removed from the driven screw so that the anvil 57 ismoved to the right under the influence of the spring 114 and as theshoulder 80 moves to the right its curved peripheral surface 122 engageswith a correspondingly shaped surface 123 of the finger 112 and so thatthe latter is moved downwardly and then is urged upwardly by the spring113 to engage behind the shoulder 80 as shown in the drawing to preventmovement of the anvil to the left until the trigger 109 is againoperated.

Referring now to FIGS. 2 and 3, these show a second embodiment of theinvention which in many respects is similar to that described in FIG. 1,where the parts of the tool shown in FIG. 2 are identical to those shownin FIG. 1 and they will only be described briefly.

In the tool of FIG. 1, the screwdriver bit 55 could only be impacted andthen rotated. With the tool of FIG. 2, the screwdriver bit of the toolcan be impacted and rotated or impacted only or rotated only.

Referring to FIG. 2, the tool has a body which is substantiallyidentical to the body 50 and mounted in the body for rotation andsliding movement relative thereto is an anvil 131 which is arranged andspring biased precisely as the anvil 57 in FIG. 1. Mounted on a bosspart 132 of the body is a holder 133 similar to the holder 86 and thisis arranged to be rotated by a nut 134 arranged identically to the nut58.

In a bore 135 in the body is mounted an impact member 136. The impactmember has a piston 137 which slides in the bore 135 and engages aresilient washer 138 through which acts a spring 139. The impact memberhas a spigot 140 which is arranged to enter a decomposition chamber orbreech 141 which communicates through a passage 142 with the outlet froma pump 143 which operates precisely as the pump 53 in FIG. 1.

Valve means indicated generally at 144 are situated in passage meansbetween the bore 141 and a chamber 145 in which the nut 134 is slidable.The passage means comprises a first passage 146 having an open end 147in the decomposition chamber, a second passage 148 which has an open end149 in tee decomposition chamber and a third passage 150 which opensinto the chamber 145. A vent 151 is provided in the decompositionchamber which is open when the valve means 144 is in one of itspositions as will be described below.

In place of the spring-loaded detent means 108 of FIG. 1, the tool ofFIG. 2 has manually operated detent means. A detent 152 is provided on alever 153 which is pivoted at 154 in the body. The end of the lever 153remote from the detent 152 is acted upon by a spring-biased ball 155tending to rotate the lever 153 in an anticlockwise direction to causethe detent 152 to engage the piston 137. Also engaging the lever 153 isone end of a pivoted rocker 156 which is pivoted at 157. A trigger 158is slidable in a slot 159 in the body against the action of a spring160. The trigger 158 carries a rod 161 to which is pivotally mounted at162 a wedge member 163. The wedge member is urged in a clockwisedirection to the position shown by means of a spring urged ball 164.

The anvil 131 carries a shoulder 165 identical to the shoulder 80 inFIG. 1 and this is engageable by a pin 166 which carries a washer 167and is urged upwardly by a spring 168. The lower end of the pin 166carries a knob 169 and a pin 170 which is received in a slot 171 in thebody. The pin 166 can be withdrawn from engagement with the shoulder165-by moving the pin downwardly by grasping the knob 169 and then whenthe pin 170 has left the slot 171 the pin 166 can be turned to cause thepin 170 to engage the external surface of the body.

The valve means 144 and the pin 166 together constitute control meanswhich can be operated so that the anvil 131 can be caused either to beimpacted and then rotated or impacted only or rotated only.

The normal arrangement is as in FIG. 1 that the anvil 131 is firstimpacted and then rotated. Assuming that this is the desired mode ofoperation, the valve means is placed in the position shown in FIG. 2 byan external knob, not shown. The pump 143 is operated to deliver acharge of monofuel into the decomposition chamber 141 as described inrelation to FIG. 1. The safety pin 166 is retracted as described aboveand is held out of engagement with the shoulder 165. The screwdriver bit172 carried by the anvil 131 is engaged with a screw to be driven andpressure is put on the tool to move the anvil 131 to the left so thatthe left-hand end 173 thereof engages the end 174 of the impact member136. The trigger 158 is then pulled which moves the rod 161 to the leftin FIG. 2 causing the wedge member 163 to pivot the rocker 156 and thuspivot the lever 153 so that the detent 152 comes out of engagement withthe piston 137.

The spring 139 then urges the impact member 136 to the left and thespigot 140 causes an explosion of the monofuel in the decompositionchamber 141. The gases produced cause the impact member 136 to return tothe position shown in the drawings thus compressing the spring 139. Theimpact member is held in this position by the detent 152 which has aninclined surface 175 and which is automatically returned to hold theimpact member in the position shown in FIG. 2 by the ticlockwisedirection and the spring-urged ball 155 holds thelever 153 in theposition shown. Thus, it does not matter if the trigger 158 is notreleased immediately since the lever 153 will return to the positionshown in FIG. 2 irrespective of whether the trigger 158 is held or not.As the impact member 136 moves to the right under the influence of thehigh pressure gases, therefore, the piston 137 will momentarily pivotthe lever 153 by engaging the inclined surface 175 but the lever willimmediately return to the position shown under the influence of thespring urged ball 155 and will hold the impact member in the positionshown. When the trigger 158 is released the rod 161 and the wedge member163 will return to the positions shown in FIG. 2 ready for the nextoperation.

As the impact member 136 returns to the position shown in FIG. 2 drivenby the high-pressure gas the ends 174 and 173 will engage and an impactwill be given to the screw engaged with the screwdriver bit 172.Moreover, the high pressure gases will be prevented from flowing throughthe first passage 146 by the valve means 144 but will flow through thepassage 148 when the end 149 thereof is uncovered by the impact memberas the latter moves to the right. When the end 149 is uncovered thegases will flow through the passages 148 and 150 into the chamber andwill cause the nut 134 to move to the right to rotate the anvil 131 inthe manner described in relation to FIG. 1. The gases will escapethrough the vent 176 and the nut will be returned to the position shownat the end of rotation. It will be seen that with this setting of thevalve means 144 and tee pin 166 the screwdriver bit 172 is given animpact and then a rotation.

In a second setting of the control means the anvil 131 is impacted only.

For impact only, the valve means 1.44 is moved to the position shown inFIG. 3a. This has two effects, firstly it seals off the passage and thusthe chamber 145 from the decomposition chamber 141 and secondly it opensthe vent 151 to atmosphere. The valve means is moved to this positionand the pin 166 is withdrawn from engagement with the shoulder asdescribed below. The screwdriver bit 172 is then engaged with a screw orother device to be impacted and the gun is pushed against the screw ordevice until the ends 173 and 174 engage. The trigger 158 is thenoperated to release the detent means as described above and the impactmember 136 moves to the left to explode the charge of monofuel which haspreviously been delivered to the decomposition chamber 141. The highpressure gases generated move the impact member 136 to the right toimpact the anvil 131 as described above and the impact member is held inthis position by the detent 152 as described. At the end of the movementof the impact member, however, the gases do not flow through thepassages to the chamber 145 but escape through the vent 151.

In a third setting of the control means, the valve means 144 is set asshown in FIG. 3(8) and the pin 166 is allowed to engage the shoulder 165as shown in FIG. 2. In this settingof the control means the anvil 131will be rotated only as will now be described. Release of the detent 152by operation of the trigger 158 will cause the impact member 136 to moveto the left and explode a charge of monofuel in the decompositionchamber 141. The passage 146 is in communication with the passage 150and therefore as soon as the gases are generated they pass to thechamber 145 to operate the nut 134. The impact member 136 returns to itsposition shown in FIG. 2 but since the pin 166 engages the shoulder 165the ends 173 and 174 do not engage and thusthe anvil 131 is notimpacted. The gases drive the nut 134 and rotate the anvil 131 throughthe holder 133 containing clutch means as described in relation toFIG. 1. The gases escape through the: vent 176 at the end of therotation.

It will be seen that the tool of FIG. 2 may be used to impact and rotatethe anvil 131 or to only impact the anvil or to only rotate the anvil.It is to be noted that the vent 151 is only open when the valve means144- is in the position shown in FIG. 3A.

Referring now to FIG. 4, this shows a modification of the tool describedin relation to FIG. 3 and in which auxiliary control means are providedto enable the anvil to be rotated first and then impacted. Parts in FIG.4 which are identical to those in FIG. 3 are indicated by the samereference numerals.

Referring to FIG. 4, the gun body 176 is provided with a chamber 177which houses the auxiliary control means. The auxiliary control meanscomprise a first lever 178 pivoted at 179 intermediate its ends. At oneend, the lever 178 carries a detent 180 which in the position shown inFIG. 4 is arranged to be engaged by an end 181 of the nut 134. The otherend of the lever 178 is pivoted at 182 to the upper end of a rod 183whose lower end is pivoted at 184 to a second lever 185. The secondlever 185 is pivoted at 186 and at its other end carries a detent 187which, in the position shown in FIG. 4, is arranged to engage the piston137 when the impact member 140 is in its left-hand position.

The left-hand end of the second lever 185 and thus the rod 183 are urgedupwardly by means of a spring urged ball 183. An operating knob 189 issecured to the upper end of an operating rod 190. The operating rodcarries a transverse pin 191 which is movable through a slot, not shown,in a plate 192 secured to the .body, the pin engaging the upper end of aspring 193.

The auxiliary control means constituted by the levers 178 and 185, therod 183 and the operating rod 190 are shown in their operative positionin FIG. 4, the transverse pin 19! having been passed through the slot inthe plate 192 and turned to hold the operating rod 190 in the positionshown.

To obtain rotation and then impact of the anvil 131 the v operating rod191) is set in the position as shown in FIG. 4 and the pin 166 iswithdrawn from the shoulder 165 as described above and the screwdriverbit 172 is engaged with the device to be driven and the tool is pushedto the right against the device so that the ends 173 and 174 engage.

The trigger 158 is now pressed thus allowing the impact member 140 tomove to the left to explode a charge of monofuel which has beendelivered to the decomposition chamber 141 from the pump 143 asdescribed above. When the impact member 140 reaches the left-hand end ofthe stroke the detent 187 engages with the piston 137 and thus holds theimpact member in this position. The gases generated by the explosionpass through the first passage 146, the valve means M4 and the thirdpassage 150 into the chamber 145. The gases move the nut 134 to the leftthus rotating the anvil 131 through the clutch in the holder 133. Beforethe nut 134 uncovers the vent 176 the end 181 engages the detent 180which pivots the lever 178 and thus the lever 185 through the rod 183thus raising the detent 187 and allowing the impact member 140 to moveto the right under the pressure of the gas so that the ends 174 and 173again come into engagement and the device engaged by the screwdriver bit172 has an impact delivered thereto. The gases escape through the vent176 and through a further vent 195 provided in the chamber 177. If it isdesired to disable the auxiliary control means so that the tool canoperate as described in relation to FIG. 3, the operating rod 190 isturned by the operating knob 189 until the pin 191 can pass through theslot and the plate 192 and can thus move the operating rod 183downwardly against the operation of the spring urged ball 188 which hasthe effect of lifting the detent 187 out of the path of the piston 137and also lifting the detent 184 out of the path of the nut 134. Theauxiliary control means can be brought back into operation by turningthe pin 191 so that it can pass through the slot in the plate 192 andlifting the control rod 190 so that the pin 191 passes through the slotand may then be turned to rest on top of the plate 192 as shown in FIG.4.

The preferred monofuel is isopropyl nitrate but if desired otherexplosivemedia such as cartridges or caseless charges could be providedand initiation of the explosion could be started by means other than thedetonation method described hereinbefore, for example the explosioncould be started by means of a spark.

I claim:

1. A power tool comprising a body, a working element mounted on the bodyfor reciprocation and rotation relative thereto, an impact membermounted in a first chamber in the body and operable to deliver impactsto the working element, a rotary drive member mounted in a secondchamber in the body and operable to rotate the working element,receiving means in the body to receive an explosive charge which, whenexploded, produces high-pressure gas in one of said chambers; open-endedpassage means extending between said chambers; and a part on the memberin said one chamber which normally covers the end of the passage meansin said chamber but which uncovers said end when said member has beenoperated by the high-pressure gas to allow the latter to flow along thepassage means to the other chamber to operate the member mountedtherein.

2. A power tool according to claim 1 wherein said one chamber is saidfirst chamber and said part is on the impact member.

3. A. power tool according to claim 2 including control meansselectively operable to any one of three settings in the first of whichthe working element is impacted and rotated by said gas and in thesecond and third of which the working element is respectively impactedonly or rotated only by said gas, the control means including valvemeans in the passage means for controlling the flow of as throu h thelatter.

4. A power tool according to c aim 3 including manually operabledisabling means forming part of said control means and including adisabling element engageable with the working element in the third stateof the control means to hold the working element out of engagement withthe impact member.

5. A power tool according to claim 3 wherein in the second setting ofthe control means the valve means prevents the flow of gas through thepassage means from the first chamber to the second chamber.

6. A power tool according to claim 5 wherein the passage means comprisesfirst, second and third passages all communicating with the valve means,the first and second passages having open ends in the first chamber,said end of the first passage being always uncovered and said end of thesecond passage being uncovered by said part, the third passage having anopen end in the second chamber and wherein in the first setting of thecontrol means the valve means seals the first passage and allowscommunication between the second and third passages, in the secondsetting of the control means the valve means seals off the thirdpassage, and in the third setting of the control means the valve meansallows communication between the first and third passages.

7. A power tool according to claim 3 wherein the control means has afourth setting in which the valve means allows the gas to flow to thesecond chamber simultaneously with its production in the first chamberand including auxiliary control means operable in said fourth setting toprevent the impact member engaging the working element under theinfluence of said gas until the latter has been rotated by the rotarydrive member.

8. A power tool according to claim 2 including detent means releaseablyto hold the impact member against the action of a spring means in acocked position, release of the detent means allowing movement of theimpact member under the influence of the spring to initiate theexplosion of a charge in said receiving means, the resultinghigh-pressure gas causing the impact member to compress the spring meansand return to its cocked position.

9. A power tool according to claim 8 wherein the detent means isspring-loaded and is rendered inoperative by an end load applied to theimpact member by the working element.

10. A power tool according to claim 9 including manually operabledisabling means including a disabling element engageable with theworking element to prevent the latter applying said end load to theimpact member unless the safety means are operated.

11. A power tool according to claim 8 wherein the detent means is springloaded to an operative position and manual release means is provided forreleasing the detent means.

12. A power tool according to claim 8 wherein the receiving means isarranged to receive a charge of a liquid monofuel, the impact membercarrying means for initiating decomposition of said fuel to produce saidexplosion.

13. A power tool according to claim 12 wherein said receiving meanscomprises a breech and said means for initiating decomposition comprisesa firing pin capable of entering the breech.

14. A power tool a according to claim 1 for use in inserting aself-tapping or -piercing screw in a workpiece and wherein the workingelement comprises a screwdriver bit.

15. A power tool according to claim 7 for use in running nuts andwherein the working element is a nut-engaging member.

1. A power tool comprising a body, a working element mounted on the bodyfor reciprocation and rotation relative thereto, an impact membermounted in a first chamber in the body and operable to deliver impactsto the working element, a rotary drive member mounted in a secondchamber in the body and operable to rotate the working element,receiving means in the body to receive an explosive charge which, whenexploded, produces high-pressure gas in one of said chambers; open-endedpassage means extending between said chambers; and a part on the memberin said one chamber which normally covers the end of the passage meansin said chamber but which uncovers said end when said member has beenoperated by the high-pressure gas to allow the latter to flow along thepassage means to the other chamber to operate the member mountedtherein.
 2. A power tool according to claim 1 wherein said one chamberis said first chamber and said part is on the impact member.
 3. A powertool according to claim 2 including control means selectively operableto any one of three settings in the first of which the working elementis impacted and rotated by said gas and in the second and third of whichthe working element is respectively impacted only or rotated only bysaid gas, the control means including valve means in the passage meansfor controlling the flow of gas through the latter.
 4. A power toolaccording to claim 3 including manually operable disabling means formingpart of said control means and including a disabling element engageablewith the working element in the third state of the control means to holdthe working element out of engagement with the impact member.
 5. A powertool according to claim 3 wherein in the second setting of the controlmeans the valve means prevents the flow of gas through the passage meansfrom the first chamber to the second chamber.
 6. A power tool accordingto claim 5 wherein the passage means comprises first, second and thirdpassages all communicating with the valve means, the first and secondpassages having open ends in the first chamber, said end of the firstpassage being always uncovered and said end of the second passage beinguncovered by said part, the third passage having an open end in thesecond chamber and wherein in the first setting of the control means thevalve means seals the first passage and allows communication between thesecond and third passages, in the second setting of the control meansthe valve means seals off the third passage, and in the third setting ofthe control means the valve means allows communication between the firstand third passages.
 7. A power tool according to claim 3 wherein thecontrol means has a fourth setting in which the valve means allows thegas to flow to the second chamber simultaneously with its production inthe first chamber and including auxiliary control means operable in saidfourth setting to prevent the impact member engaging the working elementunder the influence of said gas until the latter has been rotated by therotary drive member.
 8. A power tool according to claim 2 inclUdingdetent means releaseably to hold the impact member against the action ofa spring means in a cocked position, release of the detent meansallowing movement of the impact member under the influence of the springto initiate the explosion of a charge in said receiving means, theresulting high-pressure gas causing the impact member to compress thespring means and return to its cocked position.
 9. A power toolaccording to claim 8 wherein the detent means is spring-loaded and isrendered inoperative by an end load applied to the impact member by theworking element.
 10. A power tool according to claim 9 includingmanually operable disabling means including a disabling elementengageable with the working element to prevent the latter applying saidend load to the impact member unless the safety means are operated. 11.A power tool according to claim 8 wherein the detent means is springloaded to an operative position and manual release means is provided forreleasing the detent means.
 12. A power tool according to claim 8wherein the receiving means is arranged to receive a charge of a liquidmonofuel, the impact member carrying means for initiating decompositionof said fuel to produce said explosion.
 13. A power tool according toclaim 12 wherein said receiving means comprises a breech and said meansfor initiating decomposition comprises a firing pin capable of enteringthe breech.
 14. A power tool a according to claim 1 for use in insertinga self-tapping or -piercing screw in a workpiece and wherein the workingelement comprises a screwdriver bit.
 15. A power tool according to claim7 for use in running nuts and wherein the working element is anut-engaging member.